• 레미콘
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• no.1 s.58
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• pp.88-91
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• 1999

본 내용은 콘크리트의 품질관련 업무를 수행하는 실무자에게 도움을 주고자 레미콘 핸드북의 '레미콘의 배합설계'에서 정리 발췌한 것임

• 레미콘
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• no.10 s.57
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• pp.32-45
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• 1998

• 레미콘
• /
• no.10 s.57
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• pp.80-90
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• 1998

본 내용은 콘크리트의 품질관련 업무를 수행하는 실무자에게 도움을 주고자 레미콘 핸드북의 '레미콘의 배합설계'에서 정리 발췌한 것임

• Journal of the Korea Construction Safety Engineering Association
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• s.36
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• pp.65-72
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• 2006

• 레미콘
• /
• no.1 s.62
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• pp.37-47
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• 2000

• 레미콘
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• no.4 s.63
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• pp.77-95
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• 2000

• 레미콘
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• no.4 s.59
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• pp.36-49
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• 1999

• 레미콘
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• s.76
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• pp.43-56
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• 2003

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.811-817
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• 2006

The primary purpose of this study is to estimate the guaranteed strength and construction quality of the combined high flowing concrete which is used in the slurry wall of underground LNG storage tank. The required compressive strength of this type of concrete become generally known as a non economical value because it is applied the high addition factor for variation coefficients and low reduction factor under water concrete. Therefore, after estimation of the construction quality and guaranteed strength in actual site work, this study is to propose a suitable equation to calculate the required compressive strength in order to improve its difference. Application results in actual site work are shown as followings. The optimum nix design proportion is selected that has water-cement ratio 51%, sand-aggregate ratio 48.8%, and replacement ratio 42.6% of lime stone powder by cement weight. Test results of slump flow as construction quality give average 616~634mm. 500mm flowing time and air content are satisfied with specifications in the rage of 6.3 seconds and 4.0% respectively. Results of strength test by standard curing mold show that average compressive strength is 49.9MPa, standard deviation and variation coefficients are low as 1.66MPa and 3.36%. Also test results by cored cylinder show that average compressive strength is 66.4MPa, standard deviation and variation coefficients are low as 3.64MPa and 5.48%. The guaranteed strength ratio between standard curing mold and cored cylinder show 1.23 and 1.32 in the flanks. It is shown that applied addition factor for variation coefficients and reduction factor under water concrete to calculate the required compressive strength is proved very conservative. Therefore, based on these results, it is proposed new equation having variation coefficients 7%, addition factor 1.13 and reduction factor 0.98 under water connote.

• Journal of the Korea Concrete Institute
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• v.18 no.4 s.94
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• pp.459-467
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• 2006

Recently, interest grew on the quality of aggregates following the diminution of primary resources from river as to grow construction demand and the low grade of nature sand like sea sand. Following, need is to diversify the supply sources of fine aggregates which are excessively relying on sea sand and urgency is to find as soon as possible aggregate resources that can substitute sea sand. On the other hand, various fine aggregates are utilized to produce concrete in the domestic construction fields. However, few studies have been systematically investigated on the effects of such fine aggregates on concrete properties. Therefore, this study examined the effects of comparatively widely used fine aggregates in the domestic construction fields on the quality of concrete through the analysis of the effects of such fine aggregates on the physical properties of fresh concrete and strength of hardened concrete. Results revealed that crushed sand degraded the fluidity and air entraining of concrete compared to natural aggregates like sea sand and river sand. Especially, the use of crushed sand exhibiting bad grain shape and grade was larger adverse effect on the physical properties of concrete. The type of fine aggregates appeared to have negligible influence on the strength for W/C of 55%, 45% while crushed sand decreased the strength for W/C of 35% compared to natural aggregates. It analyzed that the combination of crushed sand exhibiting bad grain shape and grade with natural aggregates improved the characteristics of fresh concrete and had negligible influence on the strength.